With the continuous development of display technologies, liquid crystal displays (LCDs) are more and more widely used. As a LCD panel is passive light emitting device, a back light source is required to provide a light source for the LCD panel. In order to realize a better display effect, the back light source needs to use various optical films such as a light guide plate, a reflector, a diffuser plate, a prism sheet and the like.
Generally, in order to improve the display effect, it is needed to test mechanical properties (such as flatness and warpage, etc.) of optical films fabricated by different venders to evaluate and select optical films having better mechanical properties. Taking a prism sheet as an example, a conventional test needs to assemble the prism sheet module in a LCD module (including a LCD panel and a back light source) and allows the prism sheet to work in the liquid crystal display module for a period of time before taking the prism sheet out to observe whether the mechanical properties of the prism sheet are compromised.